Hi Jessica, I live in south jersey close to NJMP so, if you live down here maybe I could be a mentor as I have helped many people from time to time.
There is no Briggs World Formula anywhere around here. There was one guy many years ago but I haven’t seen him around lately. You might possibly have an ICA reed engine which was popular several years ago but has since died out.
You have a few options. You can run any engine at any event in the open class. This is a run what you brung type of thing and not serious head to head competition. You can also come out for practice days at NJMP almost any day of the week and pretty much have the track to yourself. Both are good ways to learn the sport.
If you want to get into a real race without breaking the bank I would suggest getting a used Yamaha KT100 and run in the Sr. Sportsman class at Englishtown. Please feel free to PM.